The present invention relates generally to wireless networks, and more particularly, to enhanced interference management in heterogeneous wireless networks.
The focus of this invention is on heterogeneous wireless networks (HetNets) that are expected to be fairly common and where the transmission points in the HetNet will be connected to each other by a non-ideal backhaul with a relatively high latency (ranging from 50 milliseconds to several dozens of milliseconds).
Over such HetNets, schemes that strive to obtain all coordinated resource management decisions within the fine slot-level granularity (typically a millisecond) are not suitable, since coordination (which involves exchange of messages and signaling over the backhaul) cannot be performed in such a fast manner. Instead, semi-static resource management schemes, where resource management over the set of transmission points TPs is performed at two time scales, are suitable since they are more robust towards backhaul latency.
The present invention considers one such semi-static resource management scheme. It focuses on a cluster of TPs that includes one high power macro TP and several low power pico TPs. The macro TP is the dominant interferer for all other pico TPs. The management scheme attempts to jointly exploit partial muting of the macro TP, wherein the macro TP can be made inactive for a fraction of the frame duration, and load balancing (a.k.a. user association), wherein users are associated to the TPs in that cluster, such that each user is associated to any one TP over the frame duration. The fraction for which the macro is muted can be chosen from a given finite set of fractions. This scheme requires limited coordination among TPs in the cluster which is possible under a non-ideal backhaul. The underlying coordination is performed periodically at a coarser frame-level granularity based on averaged (not instantaneous) slowly varying metrics that are relevant for a period longer than the backhaul latency. Examples of such metrics include estimates of average rates that the users can receive from those TPs under different configurations etc. On the other hand, the resource management that is done at a much finer sub-frame/slot level granularity involves no coordination among TPs and is done independently by each active TP based on fast changing information, such as instantaneous rate or SINR estimates, that is received directly by that TP from the users associated to it.
Together, partial muting of the macro transmission point TP and load balancing can lead to significant benefits.
The HetNet diagram of FIG. 1 shows 3 TPs and 3 users and associated frames. TP1 is the high power macro TP and TP2 and TP3 are the low power pico TPs. Dashed lines indicate potential association of users to TPs. TP1 is made inactive (is muted) for a fraction of the frame duration, whereas TP2 and TP3 are active throughout the frame.
Most existing works consider either exploiting only partial muting of the macro TP for a given user association or exploiting only user association for a given partial muting. Also, the prior art has adopted an approach which relaxes the underlying discrete variables, which can degrade performance.
Accordingly, there is a need for enhanced interference management in heterogeneous wireless networks.